MindCuber Troubleshooting Tips

This page includes a collection of questions, hints and tips intended
to help you solve any problems you have with MindCuber. More will be added shortly.

Please read the
General Tips
before looking at a specific section to ensure that the most likely
causes are eliminated first.

If after using this information you are still unable to resolve the
issue, please leave a message on the
MindCuber facebook page or on one of the
MindCuber videos on YouTube describing the problem
and what you have tried to resolve it.

Contents

1. General Tips

1.1 Build Instructions

This may seem obvious, but please check very carefully that MindCuber
is built exactly as shown in the build instructions. There are
several places where mistakes can easily be made that are difficult
to spot. Some of them cause unexpected problems during operation.

Several common mistakes are described in later sections.

1.2 NXT Firmware Version

Check that the latest version of firmware, 1.31, is installed on the
NXT.

If an earlier firmware version is installed, the MindCuber program
may not run correctly because it requires functions that were not
available in earlier versions or because of memory limitations.

The latest firmware is available from the
Support section of the LEGO MINDSTORMS website.. Download this firmware to the NXT using the standard LEGO MINDSTORMS software.

1.3 Executable Program Version

Check that the correct variant and latest version of the executable
program, MindCuber.rxe v2.0, has been downloaded to the NXT.
(Note: the v2.0 here refers to the software version,
not the NXT version)

If the wrong variant is used, the motors, in particular the
turntable motor, will move incorrectly because the gear ratio is
different between the two variants. The Rubik's Cube will not
turn or tilt as required

The latest version also has improved color discrimination for the most
reliable scan.

The variant and version of the program are displayed on the NXT
screen as soon as the program is run.

The version is on the top line as "MindCuber v2.0".

The variant is on the third line as "NXT 2.0"
or "NXT (Orange box)" for the 8527 variant

The latest MindCuber.rxe for NXT 8527 (orange box) or
Education Base set can be downloaded
here

(you may need to right click and select "Save link as..." depending on your browser)

1.4 Turntable Motor Alignment

When the MindCuber program is first run, the tilt arm and scan arm
are moved automatically by the program to calibrate their positions.
The turntable motor must be aligned manually.

Use the grey, left and right buttons on the NXT to carefully align
the turntable motor when the program is running and waiting for
a cube to be inserted. The motor should be aligned so that if the
turntable is pushed gently by hand it will move sligtly and
equally in each direction.

1.5 Batteries

Please try new or fully charged batteries in the NXT as several
people have reported problems that disappeared when they replaced
the batteries.

2. Scanning

MindCuber attempts to scan up to three times to try to determine
the colors of the scrambled cube. If it fails, it will report
either "Cube error" or "Scan error" at the end of the three
attempts and flash the color sensor blue or red respectively.

2.1 Message "Cube error"

This indicates that the colors appear to be correct and in the
right combination for the pieces expected on the puzzle. However,
it suggests that the cube has been taken apart and put back
together in a way that is impossible to solve only by turning
faces.

A cube will be impossible to solve normally if one corner piece
or one edge piece has been twisted or if two pieces have been
exchanged. This can happen, for exampe if the cube is taken apart
to adjust or lubricate it and put back together at random.

If this message is displayed, take the cube apart and put it back
together completly solved. The scramble it by turning the faces of
the cube as normal and try scanning again.

2.2 Message "Scan error"

Scanning may be unreliable for a number of reasons including:

The position of the color sensor is not as intended. Please
check the build instructions very carefully as some subtle
problems with parts connected in slightly the wrong place can
have a significant effect on reliability.

The battery voltage is low. Please check try new or fully
charged batteries.

The color sensor needs to be calibrated for the lighting
conditions. This is described below.

The lighting conditions are unsuitable. The color sensor
produces its own light and bright lights can interfere
with it so please try in low lighting conditions away from
direct, bright lights.

MindCuber is designed to work with the colors of a standard,
Rubik's branded cube. It has been tested with a number of
other cubes but expects one face with white stickers and the
others to be yellow, red, orange, green and blue in any order.
It has been tested successfully with several other cubes with
varying levels of reliability. Note that if the cube has black
stickers on one face instead of white, you can download and
configure the program source code to expect this.

2.3 Calibrate the Color Sensor

The color sensor is affected by a number of things such as
lighting conditions and the color of the stickers on the cube.

It can be calibrated for specific conditions by performing the
following:

Solve the white face of the Rubik's Cube

Stop the program

Start the program and then immediately press the orange button
again and hold it until the screen says "Calibrate white..."

Insert the cube into the turntable with the white face upwards

MindCuber will scan just the white face and then stop and display
three numbers on the NXT display. It saves these numbers and uses
them to calibrate the color sensor

Remove the cube, scramble it and insert it again for a normal
scan and solve